- self limiting hip disorder caused by a varying degree of ischemia and subsequent necrosis of the femoral head; 
            - avascular necrosis of nucleus of proximal femoral epiphysis, abnormal growth of the physis, and eventual remodeling of regenerated 
                  bone are the key features of this disorder; 
            - loss of blood supply to the epiphysis is thought to be the essential lesion; 
    - usually seen in 4 to 8 yr old boy with delayed skeletal maturity; 
    - male to female ratio: 4-5 to 1; 
    - rare in blacks; 
    - increased incidence with a positive family history, low birth wt, and abnormal pregnancy / delivery; 
    - upto 12% of cases are bilateral but will be at different stages & are asymmetric (vs. MED
    - ageis the key to the prognosis - after 8 yr represents poor prognosis; 





- Clinical Presentation: 
    - includes pain (often knee pain) effusion (from synovitis) & a limp; 
    - early phase: 
          - limited abduction of hip & limited internal rotation in both flexion & extension are seen; 
          - antalgic gait (due to pain); 
    - late phase: Trendelenburg gait; 


- Long Term Consequences: 
    - coxa magna 
    - coxa plana 
    - coxa breva 
    - hinged abduction: 
          - occurs when an enlarged femoral head is laterally extruded and impinges against the 
                  acetabular rim when the hip is abducted; 

























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